1. Field of the Invention
The invention relates in general to a testing technique, and more particularly, to a technique for testing whether a touch device correctly responds to a user touch.
2. Description of the Related Art
Operating interfaces of recent electronic products have become more and more user-friendly and intuitive as technology advances. For example, via a touch screen, a user can directly operate programs as well as input messages/texts/patterns with fingers or a stylus; in this way, it is much easier to convey demands than operating via traditional input devices such as a keyboard or buttons. In practice, a touch screen usually comprises a touch sensing panel and a display device disposed at the back of the touch sensing panel. According to a position of a touch on the touch sensing panel and a currently displayed image on the display device, an electronic device determines an intention of the touch to execute corresponding operations.
Current capacitive touch control techniques are in general categorized into self capacitive and mutual capacitive types. Self capacitive touch panel, featuring a single electrode structure of a simpler fabrication process and low costs, prevails in entry-level electronic devices.
FIG. 1 shows an exemplary sensing electrode arrangement of a conventional self capacitive touch panel. In a region 100, multiple sensing electrodes (e.g., an electrode 11) having an equal width and each appearing similar to a right-angle triangle are disposed. Each of the sensing electrodes is connected to a sensor (not shown). By applying a user touch, the magnetic line distribution around an electrode is affected to lead to a change in a capacitance value detected by the sensors. According to a position of the sensing electrode with the capacitance value change and an amount of the capacitance value change, a position of the user touch can be estimated.
Due to possible deviations during a fabrication process of sensing electrodes, an actual shape of the sensing electrodes may be identifiably different from an ideal shape. FIG. 2 shows two exemplary errors—a region 12A contains a disconnection, and a region 12B contains a cutaway. These errors degrade the accuracy of sensing results to even cause a misjudgment on a touch position. To prevent the foregoing problems, before being shipped out of the factory, products are required to undergo testings to filter out malfunctioning products.
In general, current testing solutions are manually performed. For example, due to conductivity of metal, a capacitance value detected by a sensor is changed when a metal rod is placed closely above a sensing electrode (e.g., as a position 30 shown in FIG. 3), which is equivalent to a user touch upon the sensing electrode. Theoretically speaking, different placement positions of the metal rod render the sensors to generate different detection results. Thus, by comparing theoretical values of the detection results with actual values, a testing staff may conclude whether the sensing electrodes correctly reflect expected capacitance changes when placing the metal rod at the corresponding position.
Further, in a current testing solution, after confirming that a normal detection result is yielded by a corresponding position tested by the metal rod, a testing staff is required to manually relocate the metal rod to another position to continue the testing procedure. Apparently, with the current testing solution, manufacturers can only randomly test a small part of products with limited human resources. Thus, a testing staff can only test few predetermined positions on touch panels under testing.